9.3.6—R = ρL / A
- Syllabus
- 9702–2028–2029
- Objective
- 9.3.6
- Level
- AS
For a uniform conductor, resistance is R=ρL/A
The resistance of a uniform conductor is R=ρL/A, where ρ is resistivity, L length and A cross-sectional area.
Use the conductor’s material through ρ, and account for geometry: longer wires resist more; thicker wires resist less.
Doubling a wire’s length doubles R, while doubling its diameter quarters R because area scales with diameter squared.
Resistivity is a material property, not the same as the resistance of one particular wire.
ConceptA-Level CAIE Physics AS